package org.apache.lucene.analysis.cn.smart;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.IOException;
import java.io.Reader;
import java.text.BreakIterator;
import java.util.Iterator;
import java.util.Locale;
import org.apache.lucene.analysis.cn.smart.hhmm.SegToken;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
import org.apache.lucene.analysis.util.SegmentingTokenizerBase;
import org.apache.lucene.util.AttributeFactory;
/**
* Tokenizer for Chinese or mixed Chinese-English text.
* <p>
* The analyzer uses probabilistic knowledge to find the optimal word segmentation for Simplified Chinese text.
* The text is first broken into sentences, then each sentence is segmented into words.
*/
public class HMMChineseTokenizer extends SegmentingTokenizerBase {
/** used for breaking the text into sentences */
private static final BreakIterator sentenceProto = BreakIterator.getSentenceInstance(Locale.ROOT);
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
private final TypeAttribute typeAtt = addAttribute(TypeAttribute.class);
private final WordSegmenter wordSegmenter = new WordSegmenter();
private Iterator<SegToken> tokens;
/** Creates a new HMMChineseTokenizer */
public HMMChineseTokenizer(Reader reader) {
this(DEFAULT_TOKEN_ATTRIBUTE_FACTORY, reader);
}
/** Creates a new HMMChineseTokenizer, supplying the AttributeFactory */
public HMMChineseTokenizer(AttributeFactory factory, Reader reader) {
super(factory, reader, (BreakIterator)sentenceProto.clone());
}
@Override
protected void setNextSentence(int sentenceStart, int sentenceEnd) {
String sentence = new String(buffer, sentenceStart, sentenceEnd - sentenceStart);
tokens = wordSegmenter.segmentSentence(sentence, offset + sentenceStart).iterator();
}
@Override
protected boolean incrementWord() {
if (tokens == null || !tokens.hasNext()) {
return false;
} else {
SegToken token = tokens.next();
clearAttributes();
termAtt.copyBuffer(token.charArray, 0, token.charArray.length);
offsetAtt.setOffset(correctOffset(token.startOffset), correctOffset(token.endOffset));
typeAtt.setType("word");
return true;
}
}
@Override
public void reset() throws IOException {
super.reset();
tokens = null;
}
}